Yeah, you have to be careful when pressurizing PVC. This is what we said in the article:

! CAUTION: DANGEROUS PROJECT

At normal temperatures, standard Schedule 40 PVC has a working pressure of around 150psi, but heat, sunlight, solvents, scratches, and time make the material lose strength, and even at the 75psi used for this project, it will eventually fail. When it fails, it will break into fragments that can be thrown with great force by the compressed air. For added safety, wear safety goggles and wrap PVC elements in several layers of duct tape (not shown) to minimize any possible shrapnel. For a bomb-proof model, you could also build the entire system out of galvanized steel pipe at a greater expense.

Nate

The sentence/paragraph immediately following the one wesc posted:

“Only one type of plastic pipe has been approved for use with compressed air. That pipe, Acrylonitrile-Butadiene-Styrene (ABS), is marked on the pipe as approved for compressed air supply.”

A little more expensive than PVC, but cheaper than galvanized steel (not to mention lighter than steel)

mehuman.myopenid.com

We are wrapping it all in duct or gorilla tape tonight and I’ll be building a wireless launch system to everyone can stand far back.

Thanks for the heads up about the ABS pipe, I was planning some other compressed air projects.